Metals can be formed by a number of processes including cold forming, warm forming and hot forming. In general cold forming is conducted on metals that are minimally heated if heated at all. The temperature of the metal rises as it is worked, even if the working occurs over a very short period of time. In general, during cold forming of a metal the metal temperature can rise to the range of from 250 to 500° F. In the process of warm forming a metal the metal is first heated in an oven and then formed at a temperature of from 600 to 1800° F. During hot forming the metal is heated to temperatures of 1900° F. and above and then worked.
Cold forming is generally carried out at a room temperature of about 75° F. and can be accomplished using a press, a stamping, or roll forming the metal into a desired shape. The metals can comprise sheets, stacked sheets, bars, billets, wires, bundled wires, pipes, tubing and rolls of metal. Many metals can be cold formed including: steels, stainless steel, aluminum, copper, brass, gold, silver and metal alloys. In one process of cold forming the metal is formed at high speed and high pressure using tool steel or carbide dies. This can be done using single hit or multiple hit tools and multiple tools with different shapes to form the final piece. The cold working of a metal increases the hardness, yield strength, and tensile strength of the formed metal part. Some cold forming processes include multiple strikes of a forming head on the metal in the same die. During cold forming operations it is important that the metal be lubricated to prevent excessive wear of the forming surfaces and tools.
Presently, a metal part to be cold formed is initially cleaned, and then a zinc phosphate conversion coating is applied to the metal. The zinc phosphate conversion coating serves to help subsequently applied lubricant coatings to adhere to the metal. The typical lubricants used include soaps, metal salts of fatty acids, such as sodium stearate. They are typically applied by dipping the part into a heated bath containing the soap. There are several issues with zinc phosphate coatings. Use of zinc phosphate adds several additional steps to the process. Prior to application of the lubricant the metal part must be cleaned, zinc phosphate treated, rinsed, and then optionally subjected to acid neutralization. After the lubricated metal part has been cold formed it is often heat treated to temper it. Prior to the heat treatment it may be necessary to remove any residual zinc phosphate and in particular any residual phosphate. This requires a hot alkaline or acidic cleaning step followed by water rinses. It is believed that any residual phosphate on the metal when it enters the heat treatment can result in the phosphate alloying with the metal surface and that these alloy sites become weak points in the metal. The presence of the phosphate may create a fracture initiation point in the metal causing loss of structural integrity and premature failure of the part. Additionally, the use of phosphate treatment solutions can result in environmental regulation burdens and waste treatment costs to the user.
It is desirable to produce a process of forming a lubricating coating on a metal prior to cold forming the metal that does not require use of zinc phosphate. It is additionally, desirable to a produce a coating that can be removed effectively from the metal after the forming process without leading to structural weaknesses in the formed metal.